Summary and conclusionsForty-seven patients at the Hospital for Sick Children, London, who had phenylketonuria and were on a lowphenylalanine diet (21 early-treated-that is, treatment started before the age of 4 months-and 26 late-treated) were placed on a normal diet between the ages of 5 and 15 years. They showed significant falls in mean IQ of about six points after the diet was withdrawn. Twenty-two similar patients (five early-treated and 17 late-treated) at the Universitats-Kinderklinik, Heidelberg, who were placed on a relaxed low-phenylalanine rather than a normal diet, showed smaller and non-significant falls in mean IQ. During the period of strict diet none of the patients in London or Heidelberg showed any consistent falls in IQ.These results suggest that complete withdrawal of the low-phenylalanine diet during childhood leads to a fall in intellectual progress in many patients.

In 1943 Kanner described a disease entity which he referred to as ‘Infantile Autism’. Creak and Ini (1960) found no evidence of psychogenic aetiology in a study of 200 parents of autistic children. Bender (1955) retrospectively studied children seen at Bellevue Hospital for behavioural or developmental disorders and who had been diagnosed as schizophrenic before seven years of age. No preponderance of the sophisticated, intelligent, well-to-do parents as described by Kanner was found; every racial and religious group was represented, Jews predominating slightly. A strong genetic predisposing factor was indicated—40 per cent of the parents were schizophrenic. Stroh (1962) insists that the child's condition cannot be attributed to maternal mishandling, and Wing (1966) has said ‘It is possible to interpret the data to support both environmental and biological theories of primary causation, but on the whole the former argument is very difficult to sustain.’

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SUMMARY A sample of 99 early treated phenylketonuric children showed higher levels of behavioural deviance than 197 matched controls. For boys this excess of behavioural deviance persisted when IQ was taken into account. For phenylketonuric girls however it was restricted to those with IQs<70. The type of behavioural deviance shown by the boys over the whole IQ range was predominantly neurotic. The levels of behavioural deviance found in phenylketonuric children were among the highest that have been reported for children with various handicapping conditions.